M31系统的外部界限：矮星系超新星与XXVIII和XXIX的动能
The Outer Limits of the M31 System: Kinematics of the Dwarf Galaxy Satellites And XXVIII and And XXIX
摘要：
我们提出了凯克/DEIMOS光谱解析恒星的M31卫星和XXVIII和XXIX。我们表明，这些可能是自约束星系的基础上18和24名成员和XXVIII和XXIX，分别。XXVIII的系统速度为-331.1 +/-1.8 km/s，速度色散为4.9+/-1.6 km/s，这意味着质光比（在r_1/2范围内）为~ 44 +/-41。XXIX的系统速度为-194.4 +/-1.5 km/s，速度色散为5.7+/-1.2 km/s，这意味着质光比（r_1/2以内）为~ 124 +/-72。And XXVIII & And XXIX的内部运动学和隐含质量与光度相当的矮椭球体（dSphs）相似，这意味着这些天体是以暗物质为主的矮星系。尽管距离宿主很远（380和188 kpc），但这些dSph的运动学表明它们是M31卫星。
英文摘要：
We present Keck/DEIMOS spectroscopy of resolved stars in the M31 satellites And XXVIII & And XXIX. We show that these are likely self-bound galaxies based on 18 and 24 members in And XXVIII & And XXIX, respectively. And XXVIII has a systemic velocity of -331.1 +/- 1.8 km/s and velocity dispersion of 4.9+/-1.6 km/s, implying a mass-to-light ratio (within r_1/2) of ~ 44 +/- 41. And XXIX has a systemic velocity of -194.4 +/- 1.5 km/s and velocity dispersion of 5.7+/-1.2 km/s, implying a mass-to-light ratio (within r_1/2) of ~ 124 +/- 72. The internal kinematics and implied masses of And XXVIII & And XXIX are similar to dwarf spheroidals (dSphs) of comparable luminosities, implying that these objects are dark matter-dominated dwarf galaxies. Despite the large projected distances from their host (380 and 188 kpc), the kinematics of these dSph suggest that they are bound M31 satellites.
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